I bought a while ago traktor pro 3 and installed it on a windows laptop. Now I am buying a macbook pro. Can I use my bought version of Traktor os must I buy a new version?
There's good news and bad news … You can use the same licence on a Mac, but support for TP3 finished with Sonoma and a new MacBook will come with Tahoe. That doesn't mean it doesn't work, just that there's no official support. It does work, but upgrading is probably a safer option.
Second this reply… same license works on both Windows & Mac.
If you end up with a second hand MacBook Pro there is no reason why you can't find an older macOS installer and roll back so it will support TP3.
Personally I have a MacBook Pro 16" 2019 i9 Intel and MacBook Pro 14" M1 Max both still on Ventura, and both have TP3 and TP4 running great.
I bought a macbook pro 14 M4, 16 gb, 512 gb, with MasOS 15 sequoia