SUSE has an in-house translations created by contracted translators in past. The work flow did not allow to merge translations between openSUSE and SLE trees up to now. It caused translation divergence. SLE Merge Robot is an output of the merge effort, and “suggests” to use SLE translation. Please review carefully, and keep standard terminology used in your language.
Initial import of yast was created from the community translations, but strings actually missing in the community translation were taken from the contracted SUSE Linux Enterprise translations. These translations are mixed in Weblate. If you are interested in the SUSE Linux Enterprise translations import review, go to ftp://ftp.suse.com/pub/people/sbrabec/yast-translations-sle-contributions/
yast2-slp-server is not part of openSUSE Leap 15. It exists only in openSUSE Tumbleweed.