As there are several software publisher reports and widgets, I'm not sure which specific one you're referring to. Lansweeper scans the publisher names as they are listed in Add/Remove Programs on the client machines though. If the publisher is not consistent with naming, there is nothing you can do at the moment to manually clean this up in Lansweeper itself. If you were to manually edit the publisher names in the Lansweeper database, your changes would be overwritten upon rescanning. The ability to manually edit the software list is on our customer wish list, but we do not have a release date for this feature.
Again, I'm not sure which report/widget you're referring to, but I do see the publisher removed from the Software Publishers widget for instance if the publisher's software is no longer installed on any computer.