Thinking about it a bit more, my feeling is that Google needed knowledge of where people went after landing on the SliQTools homepage in order to choose the sitelinks. The only way Google could have this knowledge is by using Google Analytics data. I wonder if sitelinks have ever been given to a site that did not use Analytics?
One of the search terms for which sitelinks are displayed is used by people revisiting the site to see if there is a new release. After landing on the homepage, they go to the Release History Page.
I did a rejig of the homepage a couple of weeks ago and shuffled around some of the thumbnails to make people go to a better page after the homepage, i.e. the Invoice Software page instead of the Invoices & Payments page. I think the Invoices & Payments sitelink was generated before this reshuffle. Perhaps after 90 days the sitelinks will be regenerated inline with the new site linking stucture.