Any tips / traps to avoid for starting my first open source project? (on github)

Just get it going and tidy later

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Don't expect people to contribute. It will take a very long time. (Usually years)

Just have fun with it. Put your best work forward, and be proud of it.

Choose a good license. Carefully choose a good license!
Yup een goede licentie uitkiezen voor je project is belangrijk!

If you want people to partake into he project the Readme is very very important. The more documentation on usage, contributing, installation updating you can have the better! People are more inclined to immediately leave the project page if they have to decipher the code themselves to determine how to even use your project

@Axis So true, most good github projects lack any sort of documentation and you either spend ages to understand their spaghetti stacked code or somebody wrote a documentation on his blog, but its outdated. 😐