Fraud with app purchase

I recently received an email from “We Buy Apps” declaring that this company is a startup for the marketing of apps and would be interested in buying “Periodical”. If I were ready, I would be offered something that I would not refuse.

However the conditions on the website already look quite questionable:

You sell the full and exclusive rights to the app. This includes the source code, all artwork, all assets (images, texts etc.), icons, Android credentials, web presence (social media, website etc.) and other assets of the app that are required to maintain the functionality and promotion of the app. You are selling the right to publish the app and will not be able to publish the same source code again, even under a different app name.

Continue reading

New rims on the everyday bicycle

Since I live in Berlin I drive significantly longer distances in everday life than in Augsburg. Together with the all-year use also during winter or on rainy days the rims which I laced in eraly 2015 got clearly worn out by the brakes after many thousands of kilometres of city traffic.

The new rims are again Ryde Andra 30 but now with black painting which fits the black frame of the bicycle quite well:

In contrast to the old rims I did not enlarge the valve holes and now use tubes with presta valves (also known as “french valves”) again. The tires are still relatively new and will continue to be used.

I already had a longer ride of about 42 km on the Berlin Sternfahrt 2019 with the new rims and everything worked quite well – nearly like a new bicycle :-).

I would have liked to buy the rims from a nearby bicycle dealer – however, he was unable to obtain this model with 32 and 36 holes from his wholesaler. In the end I ended up with Komponentix, who are also based in Berlin. Here I could order online and then pick up the rims on site.

Even more illegal copies of Periodical

It starts getting annoying! Another illegal copy of Periodical shows up again, this time with the name “Periodical calendar” from someone called “Eminantapps”. Currently available at

This is now the fourth case of this kind I am aware of. It’s just so easy to use existing sources and build your own app that contains advertising.

I can not really stop this happening – but I report every single case to Google and also write to the creators of these apps to delete them immediately.

As a reminder: Periodical is not public domain but has been released under the GPL! The GPL is legally binding and requires that the author of the work on which the app is based is named and that the sources of the modified version are available.

Again an illegal copy of Periodical

Unfortunately some people ignore the principles of “Open Source” and the GPL. Again I have to deal with an illegal copy of Periodical (also see Again an illegal copy of Periodical and Illegal copy of Periodical). This time it is called “Periods Tracker”, published by “joettaraubapps” (

Many thanks to Marie of for the hint via e-mail!

The procedure corresponds to the known pattern – one takes the sources, removes all references to the original and inserts advertising or offers the app as a paid version. I have already contacted “joettaraubapps” by e-mail and also sent a notice about a copyright infringement to Google.

As a reminder: The GPL is legally binding and derivative copies of my app must comply with certain conditions!

Why I don’t use WhatsApp

Recently you could read the following news at ( (translated):

WhatsApp has a vulnerability (CVE-2019-3568) that allows unauthorized remote access to the device. The attacker can simply smuggle the spyware into a device through a WhatsApp call, even if the called party does not pick it up. Since Monday evening there is a patch.

Also, there were reports last year that WhatsApp will scan messages to show personalized ads, which is probably the case now.

These and several other events of this kind (I also recall the “Cambridge Analytica” scandal on Facebook) have kept me from installing and using WhatsApp on any of my devices and I will not do that in the future.

Those who use WhatsApp should be aware that you are potentially vulnerable. On the one hand WhatsApp’s source code is not open source, so no one knows what backdoors and security vulnerabilities exist, and on the other hand WhatsApp is also an attractive target for attacks due to the huge number of users.

Alternative to WhatsApp

As an alternative I can recommend “Signal”. This is a free messenger whose sources are also disclosed and which is also recommended by security experts. Even Edward Snowden uses and recommends this app. As with WhatsApp, the mobile number for logging in and contacting other people is sufficient, whereby the operator of Signal does not have access to this data and all messages are encrypted and can only be read by the persons involved.

Continue reading

Positive feedback about Periodical

With the permission of the sender I’m honored to publish a positive feedback about Periodical, thank you very much:

Dear Mr Welzel,

I just wanted to let you know, how much I am enjoying the Periodical app for the last three months. I was using the Flo once before, but it was kinda impractical and never gave me the right information, so after I’ve read how they handle their clients’ information, I was looking for an app that will actually work for me and I found Periodical. I really enjoy how it counts the average lenght of my cycle, how I can add almost any info about my period, the minimalistic design and how it can be easily worked with.

I just wanted to thank you for your work because it trully makes my everyday life much better. Keep up the good work :)

Thank you very very much.

Rudolfová Pavla (Czech Republic)