> i have searched the archive, and something similar has been asked
before, but i did not find a solution... (and probably 'the best
licence' is not the same for everyone)
i want to:

> -encourage (re)using and building upon my patches and sharing the results.

If that's what you want, evidence suggests that the way to go is a copyleft license
like the GPL. You'd still have to decide whether you want v2, v3, v2-or-later, or
v3-or-later, but that's outside the scope of your question.

David Wheeler has written some articles on why and how the GPL encourages sharing
improvements.

> -not lock anyone (especially myself ;)) out from using
my patches in a commercial and closed 'environment' (like
a game on steam or an android/ios-app)

If that's what you want, you need a non-copyleft license like 3-clause BSD
which allows use in proprietary software.

***

If you want both at the same time, you'll need to do it manually.  That is, you
license your software as GPL for everyone, then sell exceptions to specific parties
who want to use your code in proprietary settings. To figure out the best way to
go about that you'll probably want to contact a lawyer who specializes in software
licensing.

-Jonathan