Members of the ODA consist of just about every CAD vendor in the world -- other than Autodesk -- plus another thousand or so other companies that rely on Teigha to open, maybe edit and possible save files in AutoCAD DWG, MicroStation DGN and Autodesk DXF formats. Some of them are direct competitors to Autodesk, while others want an insurance policy against Autodesk closing off independent access to the DWG format.
For the 1,400 members of the ODA, it would be financial disaster if they suddenly could not access the data they've saved in drawing files or become unable to read files provided by customers. Autodesk has its own SDK for opening and saving DWG files, which they call RealDWG, but having the ODA around keeps the second-largest CAD vendor honest. After all, it wasn't until after the ODA was established that Autodesk suddenly figured it was also a good idea to give AutoCAD free access to DWG files.
On to what's changed: Teigha 4.1 supports new features in DWG 2016 files, which is code for "supports AutoCAD 2016, which came out a couple of months ago." Also new is a graphics cache file – its job is to reduce the time it takes to regenerate the display of complex drawings by up to 80 percent, says the ODA.
Other changes include better performance for custom Web-based apps, better PDF exports and better support for mobile apps. Details on these few last items are vague.
When will your favorite non-Autodesk CAD package see these improvements? I have no idea, sorry to say. It is up to each ODA member to decide: (a) whether to implement Teigha 4.1 and (b) how much to implement. The smart ones will be doing it as quickly as possible and then trumpeting the improvements in their own press releases.