After a period of converting board and historic TBS games to computer games, companies began basing computer turn-based strategy games on completely original properties or concepts. The presence of a computer to calculate and arbitrate allows game complexity which is not feasible in a traditional board game.
A further market trend is the rise of "Indie" TBS games (games produced by small groups, independent or only somewhat affiliated with the major elements in the computer games industry). These games often extend or refine already existing TBS games. Examples include Freeciv or Golden Age of Civilizations.
Open-source games
Since turn-based strategy games do not typically require vast amounts of art or modeling, developers willing to volunteer their time can focus on gameplay. Directories like Freecode provide large lists of open-source, turn-based strategy projects.
Browser-based games
Online browser-based games do not require users to install files and are often free. The Hex Empire set of games is a good example of browser-based games in this genre.