The full text of the SDA Bible Commentaries is available at the website BibleTools.info. However, the text can only be read alongside several other commentary sources by navigating through one Bible verse at a time.
BibleTools.info includes many different commentaries, but the site is particularly useful for reading the SDA Commentaries, because they are placed at the top of page. Text can be looked up by verse or paged through one verse at a time. The portions of the SDA Bible Commentaries written by Ellen G. White are also available in multiple formats at egwwritings.org. There is no website that hosts the full commentaries in a long text format, as of 2015.