I'm not sure if that's what he means. The discussion of the point specifically mentions applications like bug trackers and wikis - not software that tends to be developed in house. Heroku is generally used for hosting applications that you wrote, rather than for hosting open source stacks developed by others (e.g. phpBB or MediaWiki).

Saying that, it all falls under the general trend of providing system administration as a service. Given how much ongoing effort is required to maintain secure, up to date and efficient servers, this is probably a good thing.