Telium’s software is an standalone product, which can run with pure Asterisk, as well as with configuration generators like Issabel, FreePBX, PIAF, etc. Telium’s software is not a plug-in module of FreePBX. (Sangoma signing applies only to FreePBX modules. ) HAAst operates between the operating system and Asterisk levels, while FreePBX operates above Asterisk as a ‘configuration generator’ that presents a pretty GUI and creates Asterisk config files for you.
You should also be aware that some companies use module signing to protect their system, while other companies use module signing solely as a way of generating profits. In the latter case any developer can have their module signed if they pay for a signing key – even a bad module which steals your data or crashes your PBX can be signed. So signing is not always meaningful, but will always increase your cost.
So module signing does not apply to HAAst, but be sure you understand the benefits really provided by module signing in the case of FreePBX.