And they should
The smallpox virus is actually too complex to reconstruct from DNA sequence. It is so big that it is almost visible under a microscope. There is a whole raft of proteins, enzymes, etc which it carries which need to made, assembled correctly and tucked onto the re-synthesized DNA. We are not there to do it just yet. So the idea of "we know the sequence, we will just reassemble it is utterly bogus. The most we can do is try to graft some material on cowpox probably creating something even more dangerous in the process.
As a number of researchers in the last decade noticed smallpox targets the same surface proteins as HIV and the "black death survivor" mutation which renders you invulnerable to HIV also affects your vulnerability to smallpox. The outburst of HIV worldwide also coincides too well with the eradication of smallpox and termination of all pox vaccination. That is by the way officially noted in the CDC analysis on the subject.
As long as we cannot rebuild it and as long as we have not figured out what is the exact relationship with HIV the stocks should stay and research should continue.
As far as it getting out of the lab it is not that easy. You can probably eat lyophilised stock from the fridge with impunity. It has to be correctly reconstituted, grown for a couple of generations on cell media to regain proper "shape" and only then it will be dangerous. The reason is exactly the same - it is a complex bugger with very complex surface proteins. If all of them are not "ticking" correctly it fails to function. Making a freshly reconstituded one with damaged surface proteins face an active immune system will in most cases lead to its elimination instead of infecting the host. Ideas like Beeb-s scarymentary "SmallPox" where the commenter says that "you can grow it on your windowsill" are utterly bogus. I used to grow viruses (less dangerous ones) in my mol biol classes and in a class of 8, 5 people actually failed that lab exercise - the virus (something out of the herpes family, forgot what it was) refused to infect the cell culture.
Good. Now let's hope they figure out exact relationship between it, HIV resistance and the black death. Pity it cannot be researched on a bigger scale.