In VoIP you don't really have exactly 8000 samples per second. You might
have 7999 in one direction and 8001 in the other. OSLEC can't tolerate
that. It needs the two directions be using EXACTLY the same sample rate.

If TDM line and VoIP rate is not same then VoIP gateway is generating/dropping some part of PCM data.

It similar to PDH device connected to SDH multiplexer and has not same clock source. Solution is elastic buffer.

http://www.reeve.com/Documents/Synchronization.pdf

The kernel is not a part of Freeswitch. The licencing of one piece of
software has not bearing on the licencing of some other piece of
software it communicates with.

So after all OSLEC is not a part of FS. You do not compile OSLEC as part of the FS.

OSLEC compiled as part of the Linux kernel. You just send the data or read data from the device driver, as well as you read or write data on the hard drive (or file system).

After all, the FS does not ask the hard disk driver (or file system) under which it was written license. Why ask echo kernel device?

Sergey