[bkury]

I wanted to check out and contribute, but git repo last commit is 4 years ago, while readme says 2.5.2, which is current version. Is it closed source now?

Current version is v2.5.2
(use the direct download link in my first post, no need to use the dev version on github right now)

A Skin is just plain XML, it can't be "closed source". If by "closed source" you mean that there is currently no public development git repository available you are right. It will be back and actively maintained once OpenHT and Night v3 are released.
 

I would also like to eventually contribute with a donation.
However, the link at github, https://www.paypal.com/paypalme/bkury, asks me to log in to PayPal or create a PayPal account. That is strange because with most PayPal.Me links, it is possible to pay directly with a card, even w/o a PayPal account...?

I'm not sure if Paypal changed that, however with the release of OpenHT & Night v3 there will also be a Patreon & Ko-fi page available. So, if you like OpenHT / Night v3 once it's released I would appreciate every support or contribution to this project because as a freelancer it really helps me to spend even more time on it. Thanks!

General Update:
I'm still working on some details, preview video will be available by the end of this month.