If you read carefully in the article provided, you will note the product they are talking about is a security kernel that provides a Linux-like interface within a type verification system similar to SecureOS which provides a BSD-like environment.

It is NOT Linux.

It is not possible for an open development product to ever be evaluated EAL7.

Note, I did not say "not easy" or even "very difficult" I said "not possible."

EAL7 also provides assurance through the use of a structured development process, development environment controls, and comprehensive TOE Evaluation assurance levels configuration management including complete automation, and evidence of secure delivery procedures.
Notice the "structured development process" bit. Considering open source development falls under Level 1 of the CMMI software development model, it cannot be considered structured under any circumstances.

Their system, on the surface appears more likely to be EAL5 at best... but we'll see. It should be noted that the system it question is not listed on the ISO-15408 "in progress list" though another EAL7 product is (but it isn't an OS).

One more point on this subject, to achieve high levels of security, such as TCSEC B3, which is more or less equal to ISO-15408 EAL6 with regard to assurance require data segregation at the hardware level, clearly this cannot be achieved with code alone. Hence:
Common Criteria EAL-7 (Evaluated Assurance Level 7), a level of certification unattained by any known OS to date.
is misleading. Even STOP 6.1.E currently the highest evaluated operating system against ISO-15408 only achieved that evaluation on the XTS-400 hardware platform.

To roughly compare ISO-15408/CC to TCSEC (with consideration to assurance levels):

EAL2 = C1
EAL4 = C2/B1
EAL5 = B2
EAL6 = B3
EAL7 = A1

And A1 evaluated systems do exist.

cheers,

catch