It's important to remember that, when Marx was writing, he was describing an emerging capitalist and industrial society. Such a society was essentially still feudal in organization, with owners and workers supplanting nobles and serfs in a still-retained structure of exploiter and exploited. The bourgeoisie in Marx was the owner class (those who owned but did not have many or any workers to exploit -- shopkeepers, basically -- were the petite-bourgeoisie).
Marx, however, never envisioned a post-industrial society where, to be sure, there are owners and workers, but there are also legions of managers and professionals who do not fit neatly into either description. He never envisioned a society with a large middle class -- a society in which an enormous number of people who were not even close to being wealthy (by their own societies standards) would nevertheless live in relative comfort -- owning homes and cars, having a reasonable amount of leisure time, and seeing their children have better lives than they had, not through revolution but through fluid class mobility. So its not surprising, I suppose, that "bourgeois" has not retained its original meaning.
As early as the 1920s, if not earlier, artists and intellectuals begin using "bourgeois" to describe not the owner class per se, but the (to their mind) pedestrian thought and artistic taste of that class. This use of bourgeois as a descriptor of taste rather than economic circumstance gets taken up, in turn, in the 1960s -- the high watermark of the American middle class -- when boomers, in rebellion against their parents, appropriate (and, to my mind, pervert) "bourgeois" and twist it to mean any embrace or defense of the status quo. Ironically, the upper class -- a/k/a the owner class, a/k/a the folks Marx originally labeled the bourgeoisie -- also start to use "bourgeois" as an insult aimed at the middle class, disparaging them for their lack of taste, class, and breeding.
So, since English is a living language, that's what "bourgeois" means now, but it's a far cry from Marx's use of the term.
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