A directive is the law. A service bulletin is the manufacturer’s own instruction, and for an experimental aircraft it is often the only guidance there is. The site finds each manufacturer’s published list, the aircraft’s own manufacturer included, and reads it again every night.
The aircraft’s Service documents page, Bulletins in its menu, shows the manufacturer’s documents that name the model. The rest of that manufacturer’s documents are folded beneath, where you can say one names another model or none. The page gives the date the list was taken and a link to the manufacturer’s own page for anything since. Each part’s card shows what its manufacturer published about that part.
Manufacturers name them differently: Service Bulletin, Service Instruction, Service Letter, Safety Directive, and more. The search treats them as the same kind of thing. Each document carries the same actions a directive does: read it and set it aside as not applicable, write it up, or recommend it to the owner.
Service bulletins are the manufacturer’s copyrighted documents. The site keeps the reference, the date and the link, never the body. The link opens the document on the manufacturer’s own site.
A service document is mandatory where an AD adopts it, or on an SLSA where the manufacturer issues it as a safety directive (14 CFR 91.327). Otherwise a write-up is your judgment that the work is needed.