This is simply a repackaging of tModLoader v0.9.2.3 with some additional compatibility files so it can continue to run for users who have had their Terraria updated to 1.3.5+ by Steam.
This does not contain the 1.3.5+ content, it contains the 1.3.4.4 content, but will actually load since 1.3.5 changed some files that prevented 0.9.2.3 from loading correctly.
Look for tModLoader 0.10 near the end of May.