That's less catastrophically flawed than I thought it would be. Having a tax-free provision for privately-owned or authorially-owned copyrights fixes my main concern with this.
What you're talking about with patents could be handled by just taxing licensing revenues. That would also work for creating a copyright value tax. However, I'm pretty sure we already have ways to tax the proceeds of copyright and patent licensing.
Also, while "buyout to uncopyright the work" is better than "buyout to own the work for yourself", I still think there's some problems with this. Public domain doesn't just mean "everyone owns it", it also means "everyone can reuse it", and when you do that you create a new copyright on that derivative work[0]. This is part and parcel of the reason why copylefts and share-alike licensing exists. It lets you lock things open. Would Microsoft be able to buy out Linus Torvalds in order to evade the GPL on Linux?
[0] This is also why nominally public domain characters like Sherlock Holmes are actually fiendishly difficult to reuse. The estate that owns the still copyrighted part of Sir Arthur Conan Doyle's work can still sue if your reuse of the public domain character is too close to their copyrighted expression. Notably, this means your Sherlock can't be too human.
I'd argue that GPL-licensed works should remain "authorial", and that each commit generates a new derivative object and, thus, a new copyright. In that sense, the "old code" goes into the public domain in ~28 years, but the "tip of tree" remains firmly GPL'd.
What you're talking about with patents could be handled by just taxing licensing revenues. That would also work for creating a copyright value tax. However, I'm pretty sure we already have ways to tax the proceeds of copyright and patent licensing.
Also, while "buyout to uncopyright the work" is better than "buyout to own the work for yourself", I still think there's some problems with this. Public domain doesn't just mean "everyone owns it", it also means "everyone can reuse it", and when you do that you create a new copyright on that derivative work[0]. This is part and parcel of the reason why copylefts and share-alike licensing exists. It lets you lock things open. Would Microsoft be able to buy out Linus Torvalds in order to evade the GPL on Linux?
[0] This is also why nominally public domain characters like Sherlock Holmes are actually fiendishly difficult to reuse. The estate that owns the still copyrighted part of Sir Arthur Conan Doyle's work can still sue if your reuse of the public domain character is too close to their copyrighted expression. Notably, this means your Sherlock can't be too human.