We've had great luck working with folks at Autodesk and through our local reseller. Generally, if you know what it is doing, and know what it needs to do instead, you can get changes made without cost very quickly by Autodesk support folks on the forums or through email.
For instance, for our Tsugami turning center we started with an existing Doosan post and we are changing M codes as they come up in posted code; I tell the Autodesk guys "it is posting an M147 for coolant through turret and I need that to be an M54, and I need bar feed torque on (M60) and off (M61) as part of the safety code in this format XXXXXXXX, and I want safe zero returns on every tool change, and it should read like this XXXXX." When spelled out like that it had been very quick for us to get the changes made. We've gone through our local reseller but honestly they just have someone from Autodesk following up it seems. For bigger changes they have folks locally here that do them.
For the Brothers, we got things changed over and now the Autodesk base post is better than what we developed. LOL
The trouble is when you've got something that is so different from any of the base posts that you might not know where to start. Since we didn't know what we'd have going in, we paid for post development that honestly we haven't used a lot of. Oh, well. Next time we'll know how to check the post library and make some test code before we buy.
You can also modify the posts yourself if you know how. Basically Java script, from the looks of it, but no one here codes. I've done simple things this way like changing the file extension name but not much else.
