The company believes that the Switch is designed to welcome outside developers.

Nintendo's relationship with third-party developers has been shaky ever since the company decided to stick to cartridges with the Nintendo 64. That was the first in a series of bizarre hardware design decisions that would require developers to go a bit out of their way to design titles for Nintendo systems. The problem peaked with the release of the Wii U which seriously suffered from a lack of third-party releases to bridge the gap between major Nintendo games.
It's a problem that Nintendo is well aware of. The question is, "What are they prepared to do about it?"
According to reports from a recent Nintendo financial meeting, Nintendo addressed this problem - in part - with the design of the Switch. According to Nintendo executive Shinya Takahashi, the Switch was designed based on Nintendo's desire to "realize an environment in which a variety of different third-party developers are able to easily develop compatible software, such as by making it compatible with Unreal and Unity as well as our own development tools.”
Essentially, then, the company intends for the Switch to be their most accessible piece of hardware in years. Shigeru Miyamoto expanded upon this position a bit by stating that, “In the current development environment, Iʼd say that it would take less than a year for them to port a PC game to Nintendo Switch.”
Furthermore, Miyamoto confirmed that Nintendo has merged their software and hardware development staffs so that the two sides can better understand what one needs from the other. On top of this, Miyamoto says that Nintendo's designers have learned to master the use of common Western video game engines used by third parties.
The one thing that will remain the same, though, is Nintendo's desire to develop console-specific software made with internal tools. Takahashi says that he believes this will "encourage third-party developers to create a number of quality software titles for Nintendo Switch.” Nintendo has been occupying that position for years now, but it does sound like they are making more concessions than ever.