To be picky, there exists no market inherently for proprietary software, only a market for software in which the only way to keep the price above zero is to use artificial scarcity via "IP", DRM, and secret source, etc.
So anyway, the correct software freedom position (what Purism is at least claiming to support) is bigger and independent from libertarianism, so if we were to have the optimal legal framework, it needs 3 things: abolish patents and copyright (not trademark though), mandate source release for published works, prohibit DRM.
So anyway, the correct software freedom position (what Purism is at least claiming to support) is bigger and independent from libertarianism, so if we were to have the optimal legal framework, it needs 3 things: abolish patents and copyright (not trademark though), mandate source release for published works, prohibit DRM.