If you work in the industry and aren't familiar with concept yet, it's something that you would greatly benefit by reading up on. Capital intensity is about the RATIO of capital costs to operating costs. Compare the cost of developing a website with the cost of operating it. In general, the former are much higher than the latter--though there are some exceptions.
Actually, the total (absolute, not the ratio) cost is related to a third factor I didn't even list--constant or increasing returns to scale. This means that products can be VERY expensive to develop before an extra dollar of investment won't result in more than one additional dollar of profit. No surprise that there's a synergistic relationship here with capital intensity (very low per-unit costs). This isn't going to be super-applicable if you're building websites for small companies, but if you consider how much it would cost to develop a commercial operating system that was on par with what's currently out there (Android/iOS/Linux/MacOS/Windows/etc...) it would many millions on the low end to billions if you couldn't rely on open source.