I know, avast DLLs are not currently signed. The original plan was to sign all files but this turned out very impractical for our daily builds as the bloody signing tools actually take VERY long, making the whole build process much slower (the problem is related with the Verisign time server - which is probably overwhelmed with requests and its response times are sometimes ridiculously long).
We may revisit this strategy for the new version (especially for "release" builds). For the time being, I'd say EXE file signing is much more important - and that's what we're doing a.t.m.
Cheers
Vlk