The floating point textures and render targets work has lived in a separate Mesa repository due to the IP being protected by external patents. This work has been done by Marek Olšák and occasionally the separate branch is re-based against Mesa master but has never been merged.
This is similar to the S3TC texture compression situation in that its developed externally as it cannot be merged into Mesa due to patents. However, the S3TC work lives as an external library (libtxc_dxtn) where as the floating point textures work is an entire branch of Mesa to be rebuilt.
What Lucas proposes is to merge the code but to have it only built if during the configure process an argument like --enable-patented. However, this option would be disabled by default and is not likely to be flipped on by any of the major distributions, due to legal reasons.
By merging this and other patented features into mainline Mesa but by blocking them with a build-time argument, it places the legal burden on the user or party compiling the code. But by merging this code into mainline Mesa it makes the code easier to maintain as it's no longer living in a third-party repository where the work needs to be occasionally re-based, is easier for interested users to obtain and enable when building Mesa, and is always up-to-date with the latest core Mesa changes, driver improvements, and other features.
The only response so far to the request to merge floating point textures has been from Intel's Eric Anholt. Eric is in support of this merge, but simply says, "I would also like to see it merged to master."