Almost all advanced technology from the HL lore is actually made by Aperture science. Cave Johnson sold that technology so that he can use the money to create lemon hand granades.

So from what I understand from old apeture they invented the portal gun back in the 50s but they continuesly tested it until the events of portal when glados killed everyone and the combine prevented anyone from wondering where did everyone who worked for aperture go the blue gel at least got sold as a stomach ace relief medicine that got banned but considering we have the gels in new apeture they continued to make the stuff for some reason the turrets I've found odd there are in universe ads for them they have packaging but you never see ruined abandoned turrets in any half life game and I recall being told that the turrets were never sold and they have a entirely separate unpacking line to get the turrets out of their packaging i honestly don't get how apeture was any compition for black mesa because black mesa at least works for the military and apeture don't sell anything they're basically valve